Climate Update 71 - May 2005

May

Climate

River flows

Soil moisture

Three-month outlook

Checkpoint

Backgrounder

Backgrounder

Backgrounder
Hail occurrence in New Zealand

Mean annual days of reported hailstorms taken from records for about 450 climate stations across New Zealand. Note that methods of observation, and the duration of reporting periods, are not consistent throughout the country.

Hailstorms are an inherent risk to primary production and other vulnerable activities throughout New Zealand. Hail records are available in New Zealand from climatological records, hourly weather reports at a few locations, and from the news media.

Checkpoint

Outlook and outcome – February 2005 to April 2005
Rainfall was below average in the north of the country, as forecast. The west of the South Island was drier than expected, and it was wetter than predicted in the southeast of the South Island.
Average to below average temperatures were expected. While average temperatures were widespread, conditions over much of the country were warmer than usual.
Streamflows were expected to be below normal in the north and east.

May

Climate Update is a summary each month of New Zealand’s climate, including soil moisture and river flows.
May 2005 – Number 71
April’s climate: April exceptionally dry and sunny. Frequent clear nights and a late southerly outbreak brought below average temperatures.
April’s river flows: Stream flows were low, especially in the north of the North Island.
Soil moisture levels: Low soil moisture in Northland.
Three-month outlook: Above average air temperatures in all districts.

Climate

New Zealand climate in April 2005
April was exceptionally dry and sunny, with near record or record low rainfall in parts of Northland, Auckland, Coromandel, Bay of Plenty, Nelson, and central Marlborough. Many locations in these regions recorded less than 10 mm of rain.
It was warmer than normal in parts of Northland, but mean temperatures were mostly below average elsewhere.

Three-month outlook

The outlook for May 2005 to July 2005
Below average sea-level pressures are expected to the south of New Zealand, with enhanced westerly or northwesterly air flows over the country. Sea surface temperatures around New Zealand are likely to be near or above average to the end of July.
Air temperatures are expected to be above average in all districts.

River flows

River flows
Low river and stream flows
Streamflows were below normal everywhere, but were particularly low in the northern North Island. Flows tended toward normal in the east of both islands.

Percentage of average April streamflows for rivers monitored in national and regional networks. The contributing catchment area above each monitoring location is shaded. NIWA field teams, regional and district councils, and hydro-power companies are thanked for providing this information.

Soil moisture

Low soil moisture in Northland
Soil moisture deficits increased in much of Northland during April. At the end of the month, moisture levels were lower than normal also in parts of western Bay of Plenty, Manawatu, Nelson, central Marlborough, and the Mackenzie District. Moisture levels were higher than normal in Hawke’s Bay, Wairarapa, and Southland.
 
Soil moisture deficit in the pasture root zone at the end of April (right) compared with the deficit at the same time last year (centre) and the long-term end of April average (left).